1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device, and more particularly to, a method for manufacturing a flash memory device.
2. Discussion of Related Art
In general, in a method for manufacturing a flash memory device, a floating gate electrode necessarily covers an active region. Therefore, an overlay margin between the active region and a first polysilicon film for the floating gate electrode is an important variable factor.
A variety of methods such as a method for forming a first polysilicon film having a gradient, a method for forming a nitride film for a hard mask of the first polysilicon film, and a method for forming offset nitride film spacers have been used to obtain the overlay margin between the active region and the first polysilicon film for the floating gate electrode.
However, the aforementioned methods have disadvantages in that the first polysilicon film is excessively thick and damaged in removal of the nitride film.
Accordingly, there are strong demands for a technology for obtaining the overlay margin between the active region and the first polysilicon film for the floating gate electrode.